"Why are the corporate special interests attacking Claire McCaskill?"asks a male narrator in the spot. "Because they want to keep getting tax breaks when they ship our jobs overseas. And Claire McCaskill is determined to stop them."

http://www.youtube.com/watch?v=PMk6_G04LCk

The ad is backed by a two-week, six-figure buy in the Kansas City and St. Louis media markets.

McCaskill will face the winner of a contentious GOP primary between Rep. Todd Akin, former state Treasurer Sarah Steelman and wealthy self-funding businessman John Brunner.